9418168 Mahoney This project will (1) continue successful geochemical work related to the Deccan Traps of India, and (2) investigate the origins of the vast but enigmatic Indian Ocean mantle domain. Recent models attribute the Deccan event to impact of the Reunion plume head beneath a fast-moving Greater India; however, a study of alkalic intrusions north of the Deccan by Basu et al. 1993 suggests that the Reunion hotspot existed at least 3 m.y. before the main Deccan eruptions. Propose to analyze a collection of Parh basalts for Nd, Pb, and Sr isotopes and ICP-MS trace elements, in order to establish whether they are indeed early Reunion hotspot products. Recent investigations have shown that modern Indian Ocean MORB, has a Pb-Nd-Sr isotopic signature quite distinct from that of Pacific and North Atlantic MORB. The earlier history of this immense mantle domain is uncertain, however, and whether it originated and grew with the breakup of Gondwana and the opening of the Indian Ocean, or is an older feature inherited from the East Tethyan Ocean asthenosphere is unknown. Propose to analyze Pb, Nd, and Sr isotopes trace elements and , where necessary, major elements from DSDP sites in the western Indian Ocean, and magmatic units of East Tethyan seafloor preserved in the Masirah, Yarlung-Zangpo, and Baluchistan ophiolites in order to answer this question.
